1. Field of the Invention
The present general inventive concept relates to an image reading device and an image forming apparatus having the same, and more particularly, to an image reading device and an image forming apparatus having the same to perform duplex (double-sided) scanning.
2. Description of the Related Art
An image forming apparatus is an apparatus that prints an image on a printing medium, e.g., paper, according to an input image signal. An image forming apparatus is classified as a printer, a copying machine, a multi-function printer which has multiple functions of printing, copying and scanning, and the like. Particularly, a multi-function printer performs a printing function of printing an image in response to image information from an external apparatus such as a computer, etc., a reading function of reading image information recorded on a document and retaining the image information in a recording medium, a copying function of printing an image in response to scanned image information, and a fax function of transmitting scanned image information to a remote place through communication links.
In order to achieve the above functions, a multi-function image forming apparatus is equipped with an image reading device which reads image information recorded on a document. An example of a conventional image reading device is disclosed in Korean Patent Laid-Open Publication No. 2004-0013444. The conventional image reading device to perform duplex (double-sided) scanning. The conventional image reading device includes a rear surface reading unit and a front surface reading unit which are sequentially arranged along a document feeding direction. The rear surface reading unit includes a white roller mounted in a document feeding path, and a contact image sensor (CIS) biased to the white roller by a constant elastic force. The rear surface reading unit reads image information recorded on a rear surface of the document passing between the white roller and the CIS. The front surface reading unit reads image information recorded on a front surface of the document through a front surface reading image sensor which is mounted at the rear of the rear surface reading unit. If a user selects a duplex (double-sided) scan mode, both the rear surface reading unit and the front surface reading unit operate so that image information recorded on both the surfaces (front surface and rear surface) of the document is scanned. If a user selects a simplex (single-sided) scan mode, either the rear surface reading unit or the front surface reading unit operates selectively so that image information recorded on only one surface (front surface or rear surface) of the document is scanned.
However, when the above conventional image reading device performs a simplex scan mode to scan image information on one surface (e.g., front surface) of the document, the white roller may be worn or the document may be damaged, because the white roller and the CIS make unnecessary friction with each other when the document passes by the rear surface reading unit. Also, when the document makes friction with the white roller or the image sensor, paper dust is generated, which may cause contamination of the image sensor and deterioration of scan quality, and may further cause contamination of other peripheral components and operational disturbance.